Arrangement for varying the band width in high frequency circuits



O 20, 19424 w. MENNERICH ETAL 2,299,337 ARRANGEMENT FOR VARYING THE BANDWIDTH IN HIGH FREQUENCY CIRCUITS j Original Filed ual cn 26, 1937 mum;

Patented Oct. 20, 1942 ARRANGEMENT FOR VARYING THE BAND WIDTH IN HIGHFREQUENCY CIRCUITS Wilhelm Mennerich, Potsdam, Otto Siepke,

Berlin-Staaken, and Alexander Schaaf, Berlin- Charlottenburg, Germany;vested in The Alien Property Custodian Original application March 26,1937, Serial No. 133,138. Divided and this application May 16, 1939,Serial No. 273,826.- In Germany.March Claims.

This application is a division of our copending application, Serial No.133,138, filed March 26, 1937, entitled Arrangement for varying thebandwidth in high frequency circuits, which application has resulted inU. S. Patent No. 2,177,835, issued October 31, 1939.

Our invention relates to an arrangement for .varying the band width inhigh-frequency circuits.

Nowadays, it is frequently necessary, particularly in radio receivedapparatus to vary the band width of the tuning devices or of the bandfilters. This isaccomplished in a manner well known in the art bydetuning the tuning circuits with respect to one another. For instance,

the band width of the circuit is adjusted and the degree of coupling orthe inductance of the tuning coils remains the same. The width of theband width will nevertheless vary with tuning of the oscillatorycircuits. While an oscillatory circuit may be adapted to be adjusted fortuning from one frequency band to another by adjustments of either thecapacity or the inductance, it is usual to change the inductance forthis purpose, inasmuch as this results in a simpler and less expensivearrangement. The band width of filters may be varied by the insertion ofcopper discs between coupled coils. The present invention uses a methodwhich is particularly advantageous, if the oscillatory circuits of thetuning device are decoupled by the interposition of elements, such astubes, and if the parts of the tuning device are placed in differentcontainers.

According to the present invention an arrangement for varying the bandwidth of tuning devices in high-frequency circuits, particularly withcompressed iron powder cores, is provided,

preferably in the case of an inductive decoupling of the tuningcircuits, by continuously varying the inductance of at least two coilsin such a manner that the inductance of one coil is reduced the sameamount as the inductance of the other coil is increased.

For a better understanding of the invention reference may be had to thefollowing description and to the instances illustrated therein. Thedetuning of the individual tuning circuits be uniformly effected. 'If,for instance, the band width is to be varied in a three tube set, two

tuning circuits are displaced in the tuning with capacitance or of theinductance of the oscillatory circuits in the following manner will benecessary as regards the wave ranges:

Per cent In the case of 150 k. c 4 In the case of 250 k. c 2.4 In thecase of 600 k. c 1 In the case of 1330 k. c 0.46

Since an influence of the capacitance of these oscillatory circuits isdifficult owing to the great differences of the detuning necessarybetween the standard and long wave range as will be apparent from theabove table and the above considerations, the inductance of thesecircuits should be influenced according to the invention,

high-frequency compressed iron powder core coils being employed for thisinstance in which besides the continuous variation of the inductance,

creased.

In the drawing accompanying the specification, Fig. 1 illustrates in ageneral manner an application of the invention to a pair of resonantcircuits; Fig. 2 illustrates one embodiment of the invention adapted foruni-control purposes; Figs. 3 and 4 illustrate methods of coupling thecores in alignment with each other; Fig. 5 illustrates the inventionapplied to circuits between a which amplifying or other electricalapparatus is towards both sides of the relative zero line is to circuitis tuned is desired, a variation of the connected; Fig. 6 illustratesdiagrammatically the application of the invention to tuning means InFigs. 1-3 this inventive idea is shown in principle. Fig. 1 showsschematically a simple band filter arrangement in the form of two coilswhich may be inductively, capacitively or galvanically coupled witheachother. In the case of oscillating coils not coupled with one another anarrangement as shown in Fig. 2 might be employed. In this embodiment,H-shaped or thread spool-shaped compressed iron powder cores of By the Athe standard wave range.

the known type are employed which permit the balance to be effected intwo ways. The coil bodies which consist of compressed iron powder corematerial are bored and are provided with a shiftable pin S. In thecasing G there is also a device which permits a further balance andwhich consists of metal or mass plates M capable of being screwed whichwhen being approached to the coil vary the inductance. Similar devicesmay, of course, also be employed in air core coils in the formofintroduced mass pins, cylinder rings and the like.

The pin balance of the embodiment is so designed that when one pin isbeing moved from the corresponding core, the pin of the other core ismoved into the latter by the same amount and that the pin of the onecore is adjusted to its maximum value if the pin of the other core hasassumed the minimum value. The pins may be connected with one another bya rod or by a guide tube of insulation material as shown in Fig. 3 andthrough a worm with the band width knob to be operated by hand. However,it is also possible to arrange the balanced pins as shown, for instance,in Fig. 4, in such a manner that they may be screwed within the coils ineither direction.

The case already mentioned as an instance, i. e., that the circuits ofthe tuning device are separated by tubes, is shown in Fig. 5 with thecorresponding Figs. 2 and 6 for compressed iron powder core arrangement.Fig. 2 shows the simple case of two separate oscillatory circuits forone wave range, whereas in Fig. 6 separate coils are provided forthelong wave range and In Fig. 6, L1 and In denote the long wave coils,whereas Miand M2 denote the standard wave coils. Each pair of coilsconsisting of a standard wave coil and a long wave coil is placed in acommon casing I and II respectively. In accordance with the percentageof the. variation of the band-width within the difierent wave rangesindicated in the above table, balance pins of different diameters areemployed in this .case in connection with the same core shape. The coilsL1 and L2 are in the instance shown equipped with pins having a largediameter, whereas pins of smaller diameter are provided for standardwave coils. In Figs. 2, 3 and 6 is indicated a way of adjusting the bandwidth as already mentioned by means of an operating knob through aspiral disc, denoted in these figures by Sp. The balance pin is soadjusted that its balancing movement takes place as far as possiblealong the straight portion of the balance curve (of. Fig. 7)

The variation of the band width according to the invention is preferablyemployed in radio sets, since in this case, as above mentioned, theabsolute amount of the band width is varied when tuning the oscillatorycircuits. In order to remove this drawback, the correction according tothe invention is, therefore, made, i. e., theband width is varied inaccordance with the tuning operative relationship'with its associatedcoil,

single means operable between two extreme positions for moving saidcores in unison with respect to said coils along said common' axis tothereby vary the inductance of all of said coils simultaneously, saidcoils and cores being arranged so that in one extreme position of saidsingle means one of the cores is substantially completely within itscoil while the other thereof is substantially wholly outside its coil,whereas, in the other extreme position of said single means the lastnamed core is substantially wholly within its coil while the other coreis substantially wholly outside its coil, and so that in anyintermediate position of said single means, at least a portion of eachcore is within its associated coil.

- 2. In signalling apparatus adapted for operation over widely separatedwave bands, individual sets of variable tuning instrumentalities .onefor each of said wave bands, one of said sets including a plurality ofcoils each coil having an individual core, another of said sets beingprovided'with a plurality of coils each coil having an individual core,all of said cores being of substantally the same length, at least one ofthe coils and its associated core of one of said sets and at least oneof the coils and its associated core of another of said sets beingproportioned relative to one another so that the ratio of the effectivediameter of said first coil to the effective diameter of its associatedcore is appreciably greater than the ratio of the diameter ofsaid othercoil to the effective diameter of its associated core and single meansfor adjusting all of said cores in unison with'respect to theirassociated coils.

3. In signalling apparatus, a first pair of coils each provided with anadjustable core of ferromagnetic material for detuning the coils toopposite sides of a mid-frequency, a second pair of coils each providedwith an adjustable core of ferro-magnetic material for detuning thelatter coils to opposite sides of a second mid-frequency, all of saidcoils being mounted end to end fashion and in coaxial relation, andsingle means for adjusting all of said cores in unison with respect IWILHELM MENNERICH. OTTO SIEPKE. ALEXANDER SCI-IAAF.

